Just back from range and first 200 rounds through new BM M-4. All new Blackhills 60 gr. SP. Open sights (ARMS flip up rear and BM Flip up front); BM 10 rounder and USGI 30's.All in all, everything went excellent! Consistent 2 - 2 1/2 inches groups at 100 yards. Consistent ejection, all cases in an 18 inch circle at 130 degrees from muzzle. NO malfunctions. Only prep I did was disassembly and clean with Tetra; dry swab the bore and shoot!!!!90 degrees & 80 % humidity today with 10 - 15 MPH wind gusts.Over all very, very pleased. Did as well as every Colt I owned or been issued.